Component-based systems must support dynamic reconfigurations to adapt to their execution context, but not at the cost of reliability. Fractal provides intrinsic support for dynamic reconfiguration, but its definition in terms of low-level APIs makes it complex to write reconfigurations and to ensure their reliability. This article presents a language-based approach to solve these issues: direct and focused language support for architecture navigation and reconfiguration make it easier both to write the reconfigurations and to ensure their reliability. Concretely, this article presents two languages: (1) FPath, a domain-specific language that provides a concise yet powerful notation to navigate inside and query Fractal architectures, and (2) FScript, a scripting language that embeds FPath and supports the definition of complex reconfigurations. FScript ensures the reliability of these reconfigurations thanks to sophisticated run-time control, which provides transactional semantics (ACID properties) to the reconfigurations.